1. Field of the Invention
The invention relates to electric motors and, more particularly, relates to electric motors having internal heat transfer mechanisms.
2. Discussion of the Related Art
Electric motors are well known for providing a central rotating shaft which can supply a rotational force to a system. Such motors generate substantial heat which must be dissipated to prevent the motors from overheating.
Two heat dissipation techniques are commonly employed, each of which exhibits several drawbacks and disadvantages. The first technique utilizes an internal fan to draw cooling air through the motor armature. This technique, while providing adequate cooling, suffers the disadvantage of drawing dust and other particulates into the motor which may harm the motor. The second technique employs an external fan to draw cooling air past the exterior of a sealed motor housing, thus providing indirect cooling. This technique is relatively inefficient because the point of heat transfer is remote from the point at which heat is generated. To compensate for this inefficiency, relatively large fans must be employed along with metal housings promoting heat transfer, thus increasing the weight and complexity of the motor.
Moreover, both of these methods suffer the disadvantage of requiring blades which are inherently noisy and inefficient. Fan blades operate by colliding with the fluid being displaced and by pushing the fluid to displace it. This type of operation creates turbulence within the fan or blower which not only creates unpleasant noise, but which also impedes the movement of the fluid through the device and reduces the overall efficiency of the device.